cartesian: look for subplot ids in fullData instead of data if present

- which is a more precise description than data,
  after than defaults step.

Author: etpinard

src/plots/cartesian/axes.js

@@ -1207,7 +1207,7 @@ axes.getSubplots = function(gd, ax) {
     var i, j, sp;
 
     // look for subplots in the data
-    var data = gd.data || [];
+    var data = gd._fullData || gd.data || [];
 
     for(i = 0; i < data.length; i++) {
         var trace = data[i];

src/plots/plots.js

@@ -569,7 +569,7 @@ plots.linkSubplots = function(newFullData, newFullLayout, oldFullData, oldFullLa
         newSubplots = newFullLayout._plots = {};
 
     var mockGd = {
-        data: newFullData,
+        _fullData: newFullData,
         _fullLayout: newFullLayout
     };